A fuel cell usually consists of a series of membrane electrode assemblies and bipolar plates stacked together in an alternating manner. The membrane electrode assembly is typically made of an ion conductive membrane sandwiched between an anode and a cathode sections each on the opposite side of the membrane. A bipolar plate is a plate-like electric conductor, having a plurality of channels for fluid passage. Reactive gases that supply to a fuel cell flow through those channels to reach the anode and cathode sections where electrochemical reactions of the gases take place, and from which electricity is produced. The electricity generated from the electrochemical reactions is collected and conducted through the bipolar plate to an external circuit. The bipolar plate, therefore, needs to have high electric conductivity or low contact resistance to reduce energy loss and heat buildup.
In the case of a hydrogen fuel cell, water management is one of the key challenges. Water is continuously generated in a hydrogen fuel cell and the ion conductive membrane needs to maintain a certain hydration level. When a hydrogen fuel cell is operated at a low current density, for example, at 0.2 A /cm2, there would not be enough gas flow to remove the water generated from the electrochemical reaction at the cathode section. Water drops can form in the fluid passages and block the supply of a reactive gas to the electrode. Without the supply of a reactant gas, the blocked section of the fuel cell will not produce electricity. Performance of the fuel cell will deteriorate due to non-homogeneous current distribution. Such phenomenon is known as low power stability (LPS).
Conventional hydrophilic coatings or treatments on a bipolar plate can improve water management, but usually adversely affect the electric contact resistance. Conventional hydrophilic coatings and treatments can also cause an increase in water leachable contaminants and electrochemical degradation of the bipolar plate, electrodes and membranes.